Method and apparatus for shuffling data

ABSTRACT

Method, apparatus, and program means for shuffling data. The method of one embodiment comprises receiving a first operand having a set of L data elements and a second operand having a set of L control elements. For each control element, data from a first operand data element designated by the individual control element is shuffled to an associated resultant data element position if its flush to zero field is not set and a zero is placed into the associated resultant data element position if its flush to zero field is not set.

This patent application is a continuation of U.S. patent applicationSer. No. 12/387,958 filed Mar. 31, 2009, which is a divisional of U.S.patent application Ser. No. 10/611,344 filed Jun. 30, 2003, nowabandoned which is a Continuation In Part application of U.S. patentapplication Ser. No. 09/952,891 filed Oct. 29, 2001, now U.S. Pat. No.7,085,795.

The patent application is related to the following: U.S. Pat. No.7,739,319, entitled “Method And Apparatus For Parallel Table LookupUsing SIMD Instructions” filed on Jul. 1, 2003; and U.S. Pat. No.7,631,025, entitled “Method And Apparatus For Rearranging Data BetweenMultiple Registers” filed on Jun. 30, 2003.

FIELD OF THE INVENTION

The present invention relates generally to the field of microprocessorsand computer systems. More particularly, the present invention relatesto a method and apparatus for shuffling data.

BACKGROUND OF THE INVENTION

Computer systems have become increasingly pervasive in our society. Theprocessing capabilities of computers have increased the efficiency andproductivity of workers in a wide spectrum of professions. As the costsof purchasing and owning a computer continues to drop, more and moreconsumers have been able to take advantage of newer and faster machines.Furthermore, many people enjoy the use of notebook computers because ofthe freedom. Mobile computers allow users to easily transport their dataand work with them as they leave the office or travel. This scenario isquite familiar with marketing staff, corporate executives, and evenstudents.

As processor technology advances, newer software code is also beinggenerated to run on machines with these processors. Users generallyexpect and demand higher performance from their computers regardless ofthe type of software being used. One such issue can arise from the kindsof instructions and operations that are actually being performed withinthe processor. Certain types of operations require more time to completebased on the complexity of the operations and/or type of circuitryneeded. This provides an opportunity to optimize the way certain complexoperations are executed inside the processor.

Media applications have been driving microprocessor development for morethan a decade. In fact, most computing upgrades in recent years havebeen driven by media applications. These upgrades have predominantlyoccurred within consumer segments, although significant advances havealso been seen in enterprise segments for entertainment enhancededucation and communication purposes. Nevertheless, future mediaapplications will require even higher computational requirements. As aresult, tomorrow's personal computing experience will be even richer inaudio-visual effects, as well as being easier to use, and moreimportantly, computing will merge with communications.

Accordingly, the display of images, as well as playback of audio andvideo data, which is collectively referred to as content, have becomeincreasingly popular applications for current computing devices.Filtering and convolution operations are some of the most commonoperations performed on content data, such as image audio and videodata. Such operations are computationally intensive, but offer a highlevel of data parallelism that can be exploited through an efficientimplementation using various data storage devices, such as for example,single instruction multiple data (SIMD) registers. A number of currentarchitectures also require unnecessary data type changes which minimizesinstruction throughput and significantly increases the number of clockcycles required to order data for arithmetic operations.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitations in the figures of the accompanying drawings, in which likereferences indicate similar elements, and in which:

FIG. 1A is a block diagram of a computer system formed with a processorthat includes execution units to execute an instruction for shufflingdata in accordance with one embodiment of the present invention;

FIG. 1B is a block diagram of another exemplary computer system inaccordance with an alternative embodiment of the present invention;

FIG. 1C is a block diagram of yet another exemplary computer system inaccordance with another alternative embodiment of the present invention;

FIG. 2 is a block diagram of the micro-architecture for a processor ofone embodiment that includes logic circuits to perform data shuffleoperations in accordance with the present invention;

FIGS. 3A-C are illustrations of shuffle masks according to variousembodiments of the present invention;

FIG. 4A is an illustration of various packed data type representationsin multimedia registers according to one embodiment of the presentinvention;

FIG. 4B illustrates packed data-types in accordance with an alternativeembodiment;

FIG. 4C illustrates one embodiment of an operation encoding (opcode)format for a shuffle instruction;

FIG. 4D illustrates an alternative operation encoding format;

FIG. 4E illustrates yet another alternative operation encoding format;

FIG. 5 is a block diagram of one embodiment of logic to perform ashuffle operation on a data operand based on a shuffle mask inaccordance with the present invention;

FIG. 6 is a block diagram of one embodiment of a circuit for performinga data shuffling operation in accordance with the present invention;

FIG. 7 illustrates the operation of a data shuffle on byte wide dataelements in accordance with one embodiment of the present invention;

FIG. 8 illustrates the operation of a data shuffle operation on wordwide data elements in accordance with another embodiment of the presentinvention;

FIG. 9 is a flow chart illustrating one embodiment of a method toshuffle data;

FIGS. 10A-H illustrate the operation of a parallel table lookupalgorithm using SIMD instructions;

FIG. 11 is a flow chart illustrating one embodiment of a method toperform a table lookup using SIMD instructions;

FIG. 12 is a flow chart illustrating another embodiment of a method toperform a table lookup;

FIGS. 13A-C illustrates an algorithm for rearranging data betweenmultiple registers;

FIG. 14 is a flow chart illustrating one embodiment of a method torearrange data between multiple registers;

FIGS. 15A-K illustrates an algorithm for shuffling data between multipleregisters to generate interleaved data; and

FIG. 16 is a flow chart illustrating one embodiment of a method toshuffle data between multiple registers to generate interleaved data.

DETAILED DESCRIPTION

A method and apparatus for shuffling data is disclosed. A method andapparatus for parallel table lookup using SIMD instructions are alsodescribed. A method and apparatus for rearranging data between multipleregisters is also disclosed. The embodiments described herein aredescribed in the context of a microprocessor, but are not so limited.Although the following embodiments are described with reference to aprocessor, other embodiments are applicable to other types of integratedcircuits and logic devices. The same techniques and teachings of thepresent invention can easily be applied to other types of circuits orsemiconductor devices that can benefit from higher pipeline throughputand improved performance. The teachings of the present invention areapplicable to any processor or machine that performs data manipulations.However, the present invention is not limited to processors or machinesthat perform 256 bit, 128 bit, 64 bit, 32 bit, or 16 bit data operationsand can be applied to any processor and machine in which shuffling ofdata is needed.

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. One of ordinary skill in theart, however, will appreciate that these specific details are notnecessary in order to practice the present invention. In otherinstances, well known electrical structures and circuits have not beenset forth in particular detail in order to not necessarily obscure thepresent invention. In addition, the following description providesexamples, and the accompanying drawings show various examples for thepurposes of illustration. However, these examples should not beconstrued in a limiting sense as they are merely intended to provideexamples of the present invention rather than to provide an exhaustivelist of all possible implementations of the present invention.

In an embodiment, the methods of the present invention are embodied inmachine-executable instructions. The instructions can be used to cause ageneral-purpose or special-purpose processor that is programmed with theinstructions to perform the steps of the present invention.Alternatively, the steps of the present invention might be performed byspecific hardware components that contain hardwired logic for performingthe steps, or by any combination of programmed computer components andcustom hardware components.

Although the below examples describe instruction handling anddistribution in the context of execution units and logic circuits, otherembodiments of the present invention can be accomplished by way ofsoftware. The present invention may be provided as a computer programproduct or software which may include a machine or computer-readablemedium having stored thereon instructions which may be used to program acomputer (or other electronic devices) to perform a process according tothe present invention. Such software can be stored within a memory inthe system. Similarly, the code can be distributed via a network or byway of other computer readable media. Thus a machine-readable medium mayinclude any mechanism for storing or transmitting information in a formreadable by a machine (e.g., a computer), but is not limited to, floppydiskettes, optical disks, Compact Disc, Read-Only Memory (CD-ROMs), andmagneto-optical disks, Read-Only Memory (ROMs), Random Access Memory(RAM), Erasable Programmable Read-Only Memory (EPROM), ElectricallyErasable Programmable Read-Only Memory (EEPROM), magnetic or opticalcards, flash memory, a transmission over the Internet, electrical,optical, acoustical or other forms of propagated signals (e.g., carrierwaves, infrared signals, digital signals, etc.) or the like.

Accordingly, the computer-readable medium includes any type ofmedia/machine-readable medium suitable for storing or transmittingelectronic instructions or information in a form readable by a machine(e.g., a computer). Moreover, the present invention may also bedownloaded as a computer program product. As such, the program may betransferred from a remote computer (e.g., a server) to a requestingcomputer (e.g., a client). The transfer of the program may be by way ofelectrical, optical, acoustical, or other forms of data signals embodiedin a carrier wave or other propagation medium via a communication link(e.g., a modem, network connection or the like).

Furthermore, embodiments of integrated circuit designs in accordancewith the present inventions can be communicated or transferred inelectronic form as a database on a tape or other machine readable media.For example, the electronic form of an integrated circuit design of aprocessor in one embodiment can be processed or manufactured via a fabto obtain a computer component. In another instance, an integratedcircuit design in electronic form can be processed by a machine tosimulate a computer component. Thus the circuit layout plans and/ordesigns of processors in some embodiments can be distributed via machinereadable mediums or embodied thereon for fabrication into a circuit orfor simulation of an integrated circuit which, when processed by amachine, simulates a processor. A machine readable medium is alsocapable of storing data representing predetermined functions inaccordance with the present invention in other embodiments.

In modern processors, a number of different execution units are used toprocess and execute a variety of code and instructions. Not allinstructions are created equal as some are quicker to complete whileothers can take an enormous number of clock cycles. The faster thethroughput of instructions, the better the overall performance of theprocessor. Thus it would be advantageous to have as many instructionsexecute as fast as possible. However, there are certain instructionsthat have greater complexity and require more in terms of execution timeand processor resources. For example, there are floating pointinstructions, load/store operations, data moves, etc.

As more and more computer systems are used in internet and multimediaapplications, additional processor support has been introduced overtime. For instance, Single Instruction, Multiple Data (SIMD)integer/floating point instructions and Streaming SIMD Extensions (SSE)are instructions that reduce the overall number of instructions requiredto execute a particular program task. These instructions can speed upsoftware performance by operating on multiple data elements in parallel.As a result, performance gains can be achieved in a wide range ofapplications including video, speech, and image/photo processing. Theimplementation of SIMD instructions in microprocessors and similar typesof logic circuit usually involve a number of issues. Furthermore, thecomplexity of SIMD operations often leads to a need for additionalcircuitry in order to correctly process and manipulate the data.

Embodiments of the present invention provide a way to implement a packedbyte shuffle instruction with a flush to zero capability as an algorithmthat makes use of SIMD related hardware. For one embodiment, thealgorithm is based on the concept of shuffling data from a particularregister or memory location based on the values of a control mask foreach data element position. Embodiments of a packed byte shuffle can beused to reduce the number of instructions required in many differentapplications that rearrange data. A packed byte shuffle instruction canalso be used for any application with unaligned loads. Embodiments ofthis shuffle instruction can be used for filtering to arrange data forefficient multiply-accumulate operations. Similarly, a packed shuffleinstruction can be used in video and encryption applications forordering data and small lookup tables. This instruction can be used tomix data from two or more registers. Thus embodiments of a packedshuffle with a flush to zero capability algorithm in accordance with thepresent invention can be implemented in a processor to support SIMDoperations efficiently without seriously compromising overallperformance.

Embodiments of the present invention provide a packed data shuffleinstruction (PSHUFB) with a flush to zero capability for efficientlyordering and arranging data of any size. In one embodiment, data isshuffled or rearranged in a register with byte granularity. The byteshuffle operation orders data sizes, which are larger than bytes, bymaintaining the relative position of bytes within the larger data duringthe shuffle operation. In addition, the byte shuffle operation canchange the relative position of data in an SIMD register and can alsoduplicate data. This PSHUFB instruction shuffles bytes from a firstsource register in accordance to the contents of shuffle control bytesin a second source register. Although the instruction permutes the data,the shuffle mask is left unaffected and unchanged during this shuffleoperation of this embodiment. The mnemonic for the one implementation is“PSHUFB register 1, register 2/memory”, wherein the first and secondoperands are SIMD registers. However, the register of the second operandcan also be replaced with a memory location. The first operand includesthe source data for shuffling. For this embodiment, the register for thefirst operand is also the destination register. Embodiments inaccordance to the present invention also include a capability of settingselected bytes to zero in addition to changing their position.

The second operand includes the set of shuffle control mask bytes todesignate the shuffle pattern. The number of bits used to select asource data element is log₂ of the number of data elements in the sourceoperand. For instance, the number of bytes in a 128 bit registerembodiment is sixteen. The log₂ of sixteen is four. Thus four bits, or anibble, is needed. The [3:0] index in the code below refers to the fourbits. If the most significant bit (MSB), bit 7 in this embodiment, ofthe shuffle control byte is set, a constant zero is written in theresult byte. If the least significant nibble of byte I of the secondoperand, the mask set, contains the integer J, then the shuffleinstruction causes the J^(th) byte of the first source register to becopied to the I^(th) byte position of the destination register. Below isexample pseudo-code for one embodiment of a packed byte shuffleoperation on 128 bit operands:

For i = 0 to 15 { if (SRC2[(i*8)+7] == 1 ) DEST[(i*8)+7...(i*8)+0] ← 0else index[3:0] ← SRC2[(i*8)+3 ... SRC2(i*8)+0] DEST[(i*8)+7...(i*8)+0]← SRC1/DEST[(index*8+7)... (index*8+0)] }

Similarly, this is example pseudo-code for another embodiment of apacked byte shuffle operation on 64 bit operands:

For i = 0 to 7 { if (SRC2[(i * 8)+7] == 1 ) DEST[(i*8)+7...(i*8)+0] ← 0else index[2:0] ← SRC2[(i*8)+2 ... SRC2(i*8)+0] DEST[(i*8)+7...(i*8)+0]← SRC1/DEST[(index*8+7)... (index*8+0)] }Note that in this 64 bit register embodiment, the lower three bits ofthe mask are used as there are eight bytes in a 64 bit register. Thelog₂ of eight is three. The [2:0] index in the code above refers to thethree bits. In alternative embodiments, the number of bits in a mask canvary to accommodate the number of data elements available in the sourcedata. For example, a mask with lower five bits is needed to select adata element in a 256 bit register.

Presently, it is somewhat difficult and tedious to rearrange data in aSIMD register. Some algorithms require more instructions to arrange datafor arithmetic operations than the actual number of instructions toexecute those operations. By implementing embodiments of a packed byteshuffle instruction in accordance with the present invention, the numberof instructions needed to achieve data rearrangement can be drasticallyreduced. For example, one embodiment of a packed byte shuffleinstruction can broadcast a byte of data to all positions of a 128 bitregister. Broadcasting data in a register is often used in filteringapplications where a single data item is multiplied by manycoefficients. Without this instruction, the data byte would have to befiltered from its source and shifted to the lowest byte position. Then,that single byte would have to be duplicated first as a byte, then thatthose two bytes duplicated again to form a doubleword, and thatdoubleword duplicated to finally form a quadword. All these operationscan be replaced with a single packed shuffle instruction.

Similarly, the reversing of all the bytes in a 128 bit register, such asin changing between big endian and little endian formats, can be easilyperformed with a single packed shuffle instruction. Whereas even thesefairly simple patterns require a number of instructions if a packedshuffle instruction were not used, complex or random patterns requireeven more inefficient instruction routines. The most straight forwardsolution to rearrange random bytes in a SIMD register is to write themto a buffer and then use integer byte reads/writes to rearrange them andread them back into a SIMD register. All these data processing wouldrequire a lengthy code sequence, while a single packed shuffleinstructions can suffice. By reducing the number of instructionsrequired, the number of clock cycles needed to produce the same resultis greatly reduced. Embodiments of the present invention also useshuffle instructions to access multiple values in a table with a SIMDinstructions. Even in the case where the a table is twice the size of aregister, algorithms in accordance with the present invention allow foraccesses to data elements at a faster rate than the one data element perinstruction as with integer operations.

FIG. 1A is a block diagram of an exemplary computer system formed with aprocessor that includes execution units to execute an instruction forshuffling data in accordance with one embodiment of the presentinvention. System 100 includes a component, such as a processor 102 toemploy execution units including logic to perform algorithms forshuffling data, in accordance with the present invention, such as in theembodiment described herein. System 100 is representative of processingsystems based on the PENTIUM® III, PENTIUM® 4, Celeron®, Xeon™,Itanium®, XScale™ and/or StrongARM™ microprocessors available from IntelCorporation of Santa Clara, Calif., although other systems (includingPCs having other microprocessors, engineering workstations, set-topboxes and the like) may also be used. In one embodiment, sample system100 may execute a version of the WINDOWS™ operating system availablefrom Microsoft Corporation of Redmond, Wash., although other operatingsystems (UNIX and Linux for example), embedded software, and/orgraphical user interfaces, may also be used. Thus, the present inventionis not limited to any specific combination of hardware circuitry andsoftware.

The present enhancement is not limited to computer systems. Alternativeembodiments of the present invention can be used in other devices suchas handheld devices and embedded applications. Some examples of handhelddevices include cellular phones, Internet Protocol devices, digitalcameras, personal digital assistants (PDAs), and handheld PCs. Embeddedapplications can include a micro controller, a digital signal processor(DSP), system on a chip, network computers (NetPC), set-top boxes,network hubs, wide area network (WAN) switches, or any other system thatperforms integer shuffle operations on operands. Furthermore, somearchitectures have been implemented to enable instructions to operate onseveral data simultaneously to improve the efficiency of multimediaapplications. As the type and volume of data increases, computers andtheir processors have to be enhanced to manipulate data in moreefficient methods.

FIG. 1A is a block diagram of a computer system 100 formed with aprocessor 102 that includes one or more execution units 108 to perform adata shuffle algorithm in accordance with the present invention. Thepresent embodiment is described in the context of a single processordesktop or server system, but alternative embodiments can be included ina multiprocessor system. System 100 is an example of a hub architecture.The computer system 100 includes a processor 102 to process datasignals. The processor 102 can be a complex instruction set computer(CISC) microprocessor, a reduced instruction set computing (RISC)microprocessor, a very long instruction word (VLIW) microprocessor, aprocessor implementing a combination of instruction sets, or any otherprocessor device, such as a digital signal processor, for example. Theprocessor 102 is coupled to a processor bus 110 that can transmit datasignals between the processor 102 and other components in the system100. The elements of system 100 perform their conventional functionsthat are well known to those familiar with the art.

In one embodiment, the processor 102 includes a Level 1 (L1) internalcache memory 104. Depending on the architecture, the processor 102 canhave a single internal cache or multiple levels of internal cache.Alternatively, in another embodiment, the cache memory can resideexternal to the processor 102. Other embodiments can also include acombination of both internal and external caches depending on theparticular implementation and needs. Register file 106 can storedifferent types of data in various registers including integerregisters, floating point registers, status registers, and instructionpointer register.

Execution unit 108, including logic to perform integer and floatingpoint operations, also resides in the processor 102. The processor 102also includes a microcode (ucode) ROM that stores microcode for certainmacroinstructions. For this embodiment, execution unit 108 includeslogic to handle a packed instruction set 109. In one embodiment, thepacked instruction set 109 includes a packed shuffle instruction fororganizing data. By including the packed instruction set 109 in theinstruction set of a general-purpose processor 102, along withassociated circuitry to execute the instructions, the operations used bymany multimedia applications may be performed using packed data in ageneral-purpose processor 102. Thus, many multimedia applications can beaccelerated and executed more efficiently by using the full width of aprocessor's data bus for performing operations on packed data. This caneliminate the need to transfer smaller units of data across theprocessor's data bus to perform one or more operations one data elementat a time.

Alternate embodiments of an execution unit 108 can also be used in microcontrollers, embedded processors, graphics devices, DSPs, and othertypes of logic circuits. System 100 includes a memory 120. Memory 120can be a dynamic random access memory (DRAM) device, a static randomaccess memory (SRAM) device, flash memory device, or other memorydevice. Memory 120 can store instructions and/or data represented bydata signals that can be executed by the processor 102.

A system logic chip 116 is coupled to the processor bus 110 and memory120. The system logic chip 116 in the illustrated embodiment is a memorycontroller hub (MCH). The processor 102 can communicate to the MCH 116via a processor bus 110. The MCH 116 provides a high bandwidth memorypath 118 to memory 120 for instruction and data storage and for storageof graphics commands, data and textures. The MCH 116 is to direct datasignals between the processor 102, memory 120, and other components inthe system 100 and to bridge the data signals between processor bus 110,memory 120, and system I/O 122. In some embodiments, the system logicchip 116 can provide a graphics port for coupling to a graphicscontroller 112. The MCH 116 is coupled to memory 120 through a memoryinterface 118. The graphics card 112 is coupled to the MCH 116 throughan Accelerated Graphics Port (AGP) interconnect 114.

System 100 uses a proprietary hub interface bus 122 to couple the MCH116 to the I/O controller hub (ICH) 130. The ICH 130 provides directconnections to some I/O devices via a local I/O bus. The local I/O busis a high-speed I/O bus for connecting peripherals to the memory 120,chipset, and processor 102. Some examples are the audio controller,firmware hub (flash BIOS) 128, wireless transceiver 126, data storage124, legacy I/O controller containing user input and keyboardinterfaces, a serial expansion port such as Universal Serial Bus (USB),and a network controller 134. The data storage device 124 can comprise ahard disk drive, a floppy disk drive, a CD-ROM device, a flash memorydevice, or other mass storage device.

For another embodiment of a system, an execution unit to execute analgorithm with a shuffle instruction can be used with a system on achip. One embodiment of a system on a chip comprises of a processor anda memory. The memory for one such system is a flash memory. The flashmemory can be located on the same die as the processor and other systemcomponents. Additionally, other logic blocks such as a memory controlleror graphics controller can also be located on a system on a chip.

FIG. 1B illustrates an alternative embodiment of a data processingsystem 140 which implements the principles of the present invention. Oneembodiment of data processing system 140 is an Intel® Personal InternetClient Architecture (Intel® PCA) applications processors with IntelXScale™ technology (as described on the world-wide web atdeveloper.intel.com). It will be readily appreciated by one of skill inthe art that the embodiments described herein can be used withalternative processing systems without departure from the scope of theinvention.

Computer system 140 comprises a processing core 159 capable ofperforming SIMD operations including a shuffle. For one embodiment,processing core 159 represents a processing unit of any type ofarchitecture, including but not limited to a CISC, a RISC or a VLIW typearchitecture. Processing core 159 may also be suitable for manufacturein one or more process technologies and by being represented on amachine readable media in sufficient detail, may be suitable tofacilitate said manufacture.

Processing core 159 comprises an execution unit 142, a set of registerfile(s) 145, and a decoder 144. Processing core 159 also includesadditional circuitry (not shown) which is not necessary to theunderstanding of the present invention. Execution unit 142 is used forexecuting instructions received by processing core 159. In addition torecognizing typical processor instructions, execution unit 142 canrecognize instructions in packed instruction set 143 for performingoperations on packed data formats. Packed instruction set 143 includesinstructions for supporting shuffle operations, and may also includeother packed instructions. Execution unit 142 is coupled to registerfile 145 by an internal bus. Register file 145 represents a storage areaon processing core 159 for storing information, including data. Aspreviously mentioned, it is understood that the storage area used forstoring the packed data is not critical. Execution unit 142 is coupledto decoder 144. Decoder 144 is used for decoding instructions receivedby processing core 159 into control signals and/or microcode entrypoints. In response to these control signals and/or microcode entrypoints, execution unit 142 performs the appropriate operations.

Processing core 159 is coupled with bus 141 for communicating withvarious other system devices, which may include but are not limited to,for example, synchronous dynamic random access memory (SDRAM) control146, static random access memory (SRAM) control 147, burst flash memoryinterface 148, personal computer memory card international association(PCMCIA)/compact flash (CF) card control 149, liquid crystal display(LCD) control 150, direct memory access (DMA) controller 151, andalternative bus master interface 152. In one embodiment, data processingsystem 140 may also comprise an I/O bridge 154 for communicating withvarious I/O devices via an I/O bus 153. Such I/O devices may include butare not limited to, for example, universal asynchronousreceiver/transmitter (UART) 155, universal serial bus (USB) 156,Bluetooth wireless UART 157 and I/O expansion interface 158.

One embodiment of data processing system 140 provides for mobile,network and/or wireless communications and a processing core 159 capableof performing SIMD operations including a shuffle operation. Processingcore 159 may be programmed with various audio, video, imaging andcommunications algorithms including discrete transformations such as aWalsh-Hadamard transform, a fast Fourier transform (FFT), a discretecosine transform (DCT), and their respective inverse transforms;compression/decompression techniques such as color space transformation,video encode motion estimation or video decode motion compensation; andmodulation/demodulation (MODEM) functions such as pulse coded modulation(PCM).

FIG. 1C illustrates yet alternative embodiments of a data processingsystem capable of performing SIMD shuffle operations. In accordance withone alternative embodiment, data processing system 160 may include amain processor 166, a SIMD coprocessor 161, a cache memory 167, and aninput/output system 168. The input/output system 168 may optionally becoupled to a wireless interface 169. SIMD coprocessor 161 is capable ofperforming SIMD operations including data shuffles. Processing core 170may be suitable for manufacture in one or more process technologies andby being represented on a machine readable media in sufficient detail,may be suitable to facilitate the manufacture of all or part of dataprocessing system 160 including processing core 170.

For one embodiment, SIMD coprocessor 161 comprises an execution unit 162and a set of register file(s) 164. One embodiment of main processor 165comprises a decoder 165 to recognize instructions of instruction set 163including SIMD shuffle instructions for execution by execution unit 162.For alternative embodiments, SIMD coprocessor 161 also comprises atleast part of decoder 165B to decode instructions of instruction set163. Processing core 170 also includes additional circuitry (not shown)which is not necessary to the understanding of the present invention.

In operation, the main processor 166 executes a stream of dataprocessing instructions that control data processing operations of ageneral type including interactions with the cache memory 167, and theinput/output system 168. Embedded within the stream of data processinginstructions are SIMD coprocessor instructions. The decoder 165 of mainprocessor 166 recognizes these SIMD coprocessor instructions as being ofa type that should be executed by an attached SIMD coprocessor 161.Accordingly, the main processor 166 issues these SIMD coprocessorinstructions (or control signals representing SIMD coprocessorinstructions) on the coprocessor bus 166 where from they are received byany attached SIMD coprocessors. In this case, the SIMD coprocessor 161will accept and execute any received SIMD coprocessor instructionsintended for it.

Data may be received via wireless interface 169 for processing by theSIMD coprocessor instructions. For one example, voice communication maybe received in the form of a digital signal, which may be processed bythe SIMD coprocessor instructions to regenerate digital audio samplesrepresentative of the voice communications. For another example,compressed audio and/or video may be received in the form of a digitalbit stream, which may be processed by the SIMD coprocessor instructionsto regenerate digital audio samples and/or motion video frames. For oneembodiment of processing core 170, main processor 166, and a SIMDcoprocessor 161 are integrated into a single processing core 170comprising an execution unit 162, a set of register file(s) 164, and adecoder 165 to recognize instructions of instruction set 163 includingSIMD shuffle instructions.

FIG. 2 is a block diagram of the micro-architecture for a processor 200of one embodiment that includes logic circuits to perform shuffleoperations in accordance with the present invention. The shuffleoperation may also be referred to as a packed data shuffle operation andpacked shuffle instruction as in the discussion above. For oneembodiment of the shuffle instruction, the instruction can shufflepacked data with a byte granularity. That instruction can also bereferred to as PSHUFB or packed shuffle byte. In other embodiments, theshuffle instruction can also be implemented to operate on data elementshaving sizes of word, doubleword, quadword, etc. The in-order front end201 is the part of the processor 200 that fetches the macro-instructionsto be executed and prepares them to be used later in the processorpipeline. The front end 201 of this embodiment includes several units.The instruction prefetcher 226 fetches macro-instructions from memoryand feeds them to an instruction decoder 228 which in turn decodes theminto primitives called micro-instructions or micro-operations (alsocalled micro op or uops) that the machine know how to execute. The tracecache 230 takes decoded uops and assembles them into program orderedsequences or traces in the uop queue 234 for execution. When the tracecache 230 encounters a complex macro-instruction, the microcode ROM 232provides the uops needed to complete the operation.

Many macro-instructions are converted into a single micro-op, and othersneed several micro-ops to complete the full operation. In thisembodiment, if more than four micro-ops are needed to complete amacro-instruction, the decoder 228 accesses the microcode ROM 232 to dothe macro-instruction. For one embodiment, a packed shuffle instructioncan be decoded into a small number of micro ops for processing at theinstruction decoder 228. In another embodiment, an instruction for apacked data shuffle algorithm can be stored within the microcode ROM 232should a number of micro-ops be needed to accomplish the operation. Thetrace cache 230 refers to a entry point programmable logic array (PLA)to determine a correct micro-instruction pointer for reading themicro-code sequences for the shuffle algorithms in the micro-code ROM232. After the microcode ROM 232 finishes sequencing micro-ops for thecurrent macro-instruction, the front end 201 of the machine resumesfetching micro-ops from the trace cache 230.

Some SIMD and other multimedia types of instructions are consideredcomplex instructions. Most floating point related instructions are alsocomplex instructions. As such, when the instruction decoder 228encounters a complex macro-instruction, the microcode ROM 232 isaccessed at the appropriate location to retrieve the microcode sequencefor that macro-instruction. The various micro-ops needed for performingthat macro-instruction are communicated to the out-of-order executionengine 203 for execution at the appropriate integer and floating pointexecution units.

The out-of-order execution engine 203 is where the micro-instructionsare prepared for execution. The out-of-order execution logic has anumber of buffers to smooth out and re-order the flow ofmicro-instructions to optimize performance as they go down the pipelineand get scheduled for execution. The allocator logic allocates themachine buffers and resources that each uop needs in order to execute.The register renaming logic renames logic registers onto entries in aregister file. The allocator also allocates an entry for each uop in oneof the two uop queues, one for memory operations and one for non-memoryoperations, in front of the instruction schedulers: memory scheduler,fast scheduler 202, slow/general floating point scheduler 204, andsimple floating point scheduler 206. The uop schedulers 202, 204, 206,determine when a uop is ready to execute based on the readiness of theirdependent input register operand sources and the availability of theexecution resources the uops need to complete their operation. The fastscheduler 202 of this embodiment can schedule on each half of the mainclock cycle while the other schedulers can only schedule once per mainprocessor clock cycle. The schedulers arbitrate for the dispatch portsto schedule uops for execution.

Register files 208, 210, sit between the schedulers 202, 204, 206, andthe execution units 212, 214, 216, 218, 220, 222, 224 in the executionblock 211. There is a separate register file 208, 210, for integer andfloating point operations, respectively. Each register file 208, 210, ofthis embodiment also includes a bypass network that can bypass orforward just completed results that have not yet been written into theregister file to new dependent uops. The integer register file 208 andthe floating point register file 210 are also capable of communicatingdata with the other. For one embodiment, the integer register file 208is split into two separate register files, one register file for the loworder 32 bits of data and a second register file for the high order 32bits of data. The floating point register file 210 of one embodiment has128 bit wide entries because floating point instructions typically haveoperands from 64 to 128 bits in width.

The execution block 211 contains the execution units 212, 214, 216, 218,220, 222, 224, where the instructions are actually executed. Thissection includes the register files 208, 210, that store the integer andfloating point data operand values that the micro-instructions need toexecute. The processor 200 of this embodiment is comprised of a numberof execution units: address generation unit (AGU) 212, AGU 214, fast ALU216, fast ALU 218, slow ALU 220, floating point ALU 222, floating pointmove unit 224. For this embodiment, the floating point execution blocks222, 224, execute floating point, MMX, SIMD, and SSE operations. Thefloating point ALU 222 of this embodiment includes a floating pointdivider to execute divide, square root, and remainder micro-ops. Forembodiments of the present invention, any act involving a floating pointvalue occurs with the floating point hardware. For example, conversionsbetween integer format and floating point format involve a floatingpoint register file. Similarly, a floating point divide operationhappens at a floating point divider. On the other hand, non-floatingpoint numbers and integer type are handled with integer hardwareresources. The simple, very frequent ALU operations go to the high-speedALU execution units 216, 218. The fast ALUs 216, 218, of this embodimentcan execute fast operations with an effective latency of half a clockcycle. For one embodiment, most complex integer operations go to theslow ALU 220 as the slow ALU 220 includes integer execution hardware forlong latency type of operations, such as a multiplier, shifts, flaglogic, and branch processing. Memory load/store operations are executedby the AGUs 212, 214. For this embodiment, the integer ALUs 216, 218,220, are described in the context of performing integer operations on 64bit data operands. In alternative embodiments, the ALUs 216, 218, 220,can be implemented to support a variety of data bits including 16, 32,128, 256, etc. Similarly, the floating point units 222, 224, can beimplemented to support a range of operands having bits of variouswidths. For one embodiment, the floating point units 222, 224, canoperate on 128 bits wide packed data operands in conjunction with SIMDand multimedia instructions.

In this embodiment, the uops schedulers 202, 204, 206, dispatchdependent operations before the parent load has finished executing. Asuops are speculatively scheduled and executed in processor 200, theprocessor 200 also includes logic to handle memory misses. If a dataload misses in the data cache, there can be dependent operations inflight in the pipeline that have left the scheduler with temporarilyincorrect data. A replay mechanism tracks and re-executes instructionsthat use incorrect data. Only the dependent operations need to bereplayed and the independent ones are allowed to complete. Theschedulers and replay mechanism of one embodiment of a processor arealso designed to catch instruction sequences for shuffle operations.

The term “registers” is used herein to refer to the on-board processorstorage locations that are used as part of macro-instructions toidentify operands. In other words, the registers referred to herein arethose that are visible from the outside of the processor (from aprogrammer's perspective). However, the registers of an embodimentshould not be limited in meaning to a particular type of circuit.Rather, a register of an embodiment need only be capable of storing andproviding data, and performing the functions described herein. Theregisters described herein can be implemented by circuitry within aprocessor using any number of different techniques, such as dedicatedphysical registers, dynamically allocated physical registers usingregister renaming, combinations of dedicated and dynamically allocatedphysical registers, etc. In one embodiment, integer registers store 32bit integer data. A register file of one embodiment also contains eightmultimedia SIMD registers for packed data. For the discussions below,the registers are understood to be data registers designed to holdpacked data, such as 64 bits wide MMX™ registers (also referred to as‘mm’ registers in some instances) in microprocessors enabled with MMXtechnology from Intel Corporation of Santa Clara, Calif. These MMXregisters, available in both integer and floating point forms, canoperated with packed data elements that accompany SIMD and SSEinstructions. Similarly, 128 bits wide XMM registers relating to SSE2technology can also be used to hold such packed data operands. In thisembodiment, in storing packed data and integer data, the registers donot need to differentiate between the two data types.

In the examples of the following figures, a number of data operands aredescribed. For simplicity, the initial source data segments are labeledfrom letter A onwards alphabetically, wherein A is located at the lowestaddress and Z would be located at the highest address. Thus, A mayinitially be at address 0, B at address 1 C at address 3, and so on.Conceptually, a shuffle operation, as in the packed byte shuffle for oneembodiment, entails shuffling data segments from a first operand andrearranging one or more of the source data elements into a patternspecified by a set of masks in a second operand. Thus, a shuffle canrotate or completely rearrange a portion of or all of the data elementsinto any desired order. Furthermore, any particular data element ornumber of data elements can be duplicated or broadcasted in theresultant. Embodiments of the shuffle instruction in accordance with thepresent invention include a flush to zero functionality wherein the maskfor each particular data element can cause that data element position tobe zeroed out in the resultant.

FIGS. 3A-C are illustrations of shuffle masks according to variousembodiments of the present invention. A packed data operand 310comprised of a plurality of individual data elements 311, 312, 313, 314,is shown in this example. The packed operand 310 of this example isdescribed in the context of a packed data operand for containing a setof masks to indicate a shuffle pattern for corresponding packed dataelements of another operand. Thus, the mask in each of the data elements311, 312, 313, 314, of packed operand 310 designates the contents in thecorresponding data element position of the resultant. For example, dataelement 311 is in the leftmost data element position. The mask in dataelement 311 is to designate what data should be shuffled or placed inthe leftmost data element position of the resultant for the shuffleoperation. Similarly, data element 312 is the second leftmost dataelement position. The mask in data element 312 is to designate what datashould be placed in the second leftmost data element position of theresultant. For this embodiment, each of the data elements in the packedoperand containing the shuffle masks has a one to one correspondence toa data element position in the packed resultant.

In FIG. 3A, data element 312 used to describe the contents of an exampleshuffle mask for one embodiment. The shuffle mask 318 for one embodimentis comprised of three portions: a ‘set to zero flag’ field 315, a‘reserved’ field 316, and a ‘selections bits’ field 317. The ‘set tozero flag’ field 315 is to indicate whether the resultant data elementposition designated by the present mask should be zeroed out, or inother words, replaced with a value of zero (‘0’). In one embodiment, the‘set to zero flag’ field is dominant wherein if the ‘set to zero flag’field 315 is set, the rest of the fields in the mask 318 are ignored andthe resultant data element position is filled with ‘0’. The ‘reserved’field 316 includes one or more bits that may or may not be used inalternative embodiments or may have been reserved for future or specialuse. The ‘selection bits’ field 317 of this shuffle mask 318 is todesignate the source of the data for the corresponding data elementposition in the packed resultant.

For one embodiment of a packed data shuffle instruction, one operand iscomprised of a set of masks and another operand is comprised of a set ofpacked data elements. Both operands are of the same size. Depending onthe number of the data elements in the operands, a varying number ofselection bits are needed to select an individual data element from thesecond packed data operand for placement in the packed resultant. Forexample, with a 128 bit source operand of packed bytes, at least fourselection bits are needed as sixteen byte data elements are availablefor selection. Based on the value indicated by the selection bits of themask, the appropriate data element from the source data operand isplaced in the corresponding data element position for that mask. Forexample, the mask 318 of data element 312 corresponds to the secondleftmost data element position. If the selection bits 317 of this mask318 contain a value of ‘X’, the data element from data element position‘X’ in the source data operand is shuffled into the second leftmost dataelement position in the resultant. But if the ‘set to zero flag’ field315 is set, the second leftmost data element position in the resultantis replaced with ‘0’ and the designation of the selection bits 317ignored.

FIG. 3B illustrates the structure of a mask 328 for one embodiment thatoperates with byte size data elements and 128 bit wide packed operands.For this embodiment, the ‘set to zero’ field 325 is comprised of bit 7and the ‘selection’ field 327 is comprised of bits 3 through 0 as thereare sixteen possible data element selections. Bits 6 through 4 are notused in this embodiment and reside in the ‘reserved’ field 326. Inanother embodiment, the number of bits used in the ‘selection’ field 327can be increased or decreased as needed in order to accommodate thenumber of possible data element selections available in the source dataoperand.

FIG. 3C illustrates the structure of a mask 338 for another embodimentthat operates with byte size data elements and 128 bit wide packedoperands, but with multiple data element sources. In this embodiment,the mask 338 is comprised of a ‘set to zero’ field 335, a ‘source (src)select’ field 336, and a ‘selection’ field 337. The ‘set to zero’ field335 and ‘selection’ field 337 function similar to the descriptionsabove. The ‘source select’ field 336 of this embodiment is to indicatefrom which data source the data operand specified by the selection bitsshould be obtained. For example, the same set of masks may be used withmultiple data sources such as a plurality of multimedia registers. Eachsource multimedia register is assigned a numeric value and the value inthe ‘source select’ field 336 points to one of these source registers.Depending on the contents of the ‘source select’ field 336, the selecteddata element is selected from the appropriate data source for placementat that corresponding data element position in the packed resultant.

FIG. 4A is an illustration of various packed data type representationsin multimedia registers according to one embodiment of the presentinvention. FIG. 4A illustrates a data types for packed byte 410, packedword 420, and a packed doubleword (dword) 430 for 128 bits wideoperands. The packed byte format 410 of this example is 128 bits longand contains sixteen packed byte data elements. A byte is defined hereas 8 bits of data. Information for each byte data element is stored inbit 7 through bit 0 for byte 0, bit 15 through bit 8 for byte 1, bit 23through bit 16 for byte 2, and finally bit 120 through bit 127 for byte15. Thus, all available bits are used in the register. This storagearrangement increases the storage efficiency of the processor. As well,with sixteen data elements accessed, one operation can now be performedon sixteen data elements in parallel.

Generally, a data element is an individual piece of data that is storedin a operand (single register or memory location) with other dataelements of the same length. In packed data sequences relating to SSE2technology, the number of data elements stored in an operand (XMMregister or memory location) is 128 bits divided by the length in bitsof an individual data element. Similarly, in packed data sequencesrelating to MMX and SSE technology, the number of data elements storedin an operand (MMX register or memory location) is 64 bits divided bythe length in bits of an individual data element. The packed word format420 of this example is 128 bits long and contains eight packed word dataelements. Each packed word contains sixteen bits of information. Thepacked doubleword format 430 of FIG. 4A is 128 bits long and containsfour packed doubleword data elements. Each packed doubleword dataelement contains thirty two bits of information. A packed quadword is128 bits long and contains two packed quad-word data elements.

FIG. 4B illustrates alternative in-register data storage formats. Eachpacked data can include more than one independent data element. Threepacked data formats are illustrated; packed half 441, packed single 442,and packed double 443. One embodiment of packed half 441, packed single442, and packed double 443 contain fixed-point data elements. For analternative embodiment one or more of packed half 441, packed single442, and packed double 443 may contain floating-point data elements. Onealternative embodiment of packed half 441 is one hundred twenty-eightbits long containing eight 16-bit data elements. One embodiment ofpacked single 442 is one hundred twenty-eight bits long and containsfour 32-bit data elements. One embodiment of packed double 443 is onehundred twenty-eight bits long and contains two 64-bit data elements. Itwill be appreciated that such packed data formats may be furtherextended to other register lengths, for example, to 96-bits, 160-bits,192-bits, 224-bits, 256-bits or more.

FIG. 4C is a depiction of one embodiment of an operation encoding(opcode) format 460, having thirty-two or more bits, and register/memoryoperand addressing modes corresponding with a type of opcode formatdescribed in the “IA-32 Intel Architecture Software Developer's ManualVolume 2: Instruction Set Reference,” which is which is available fromIntel Corporation, Santa Clara, Calif. on the world-wide-web (www) atintel.com/design/litcentr. The type of shuffle operation, may be encodedby one or more of fields 461 and 462. Up to two operand locations perinstruction may be identified, including up to two source operandidentifiers 464 and 465. For one embodiment of a shuffle instruction,destination operand identifier 466 is the same as source operandidentifier 464. For an alternative embodiment, destination operandidentifier 466 is the same as source operand identifier 465. Therefore,for embodiments of a shuffle operation, one of the source operandsidentified by source operand identifiers 464 and 465 is overwritten bythe results of the shuffle operations. For one embodiment of the shuffleinstruction, operand identifiers 464 and 465 may be used to identify64-bit source and destination operands.

FIG. 4D is a depiction of another alternative operation encoding(opcode) format 470, having forty or more bits. Opcode format 470corresponds with opcode format 460 and comprises an optional prefix byte478. The type of shuffle operation, may be encoded by one or more offields 478, 471, and 472. Up to two operand locations per instructionmay be identified by source operand identifiers 474 and 475 and byprefix byte 478. For one embodiment of the shuffle instruction, prefixbyte 478 may be used to identify 128-bit source and destinationoperands. For one embodiment of the shuffle instruction, destinationoperand identifier 476 is the same as source operand identifier 474. Foran alternative embodiment, destination operand identifier 476 is thesame as source operand identifier 475. Therefore, for embodiments ofshuffle operations, one of the source operands identified by sourceoperand identifiers 474 and 475 is overwritten by the results of theshuffle operations. Opcode formats 460 and 470 allow register toregister, memory to register, register by memory, register by register,register by immediate, register to memory addressing specified in partby MOD fields 463 and 473 and by optional scale-index-base anddisplacement bytes.

Turning next to FIG. 4E, in some alternative embodiments, 64 bit singleinstruction multiple data (SIMD) arithmetic operations may be performedthrough a coprocessor data processing (CDP) instruction. Operationencoding (opcode) format 480 depicts one such CDP instruction having CDPopcode fields 482 and 489. The type of CDP instruction, for alternativeembodiments of shuffle operations, may be encoded by one or more offields 483, 484, 487, and 488. Up to three operand locations perinstruction may be identified, including up to two source operandidentifiers 485 and 490 and one destination operand identifier 486. Oneembodiment of the coprocessor can operate on 8, 16, 32, and 64 bitvalues. For one embodiment, the shuffle operation is performed onfixed-point or integer data elements. In some embodiments, a shuffleinstruction may be executed conditionally, using condition field 481.For some shuffle instructions source data sizes may be encoded by field483. In some embodiments of a shuffle instruction, Zero (Z), negative(N), carry (C), and overflow (V) detection can be done on SIMD fields.For some instructions, the type of saturation may be encoded by field484.

FIG. 5 is a block diagram of one embodiment of logic to perform ashuffle operation on a data operand based on a shuffle mask inaccordance with the present invention. The instruction (PSHUFB) forshuffle operation with a set to zero capability of this embodimentbegins with two pieces of information a first (mask) operand 510 and asecond (data) operand 520. For the following discussions, MASK, DATA,and RESULTANT are generally referred to as operands or data blocks, butnot restricted as such, and also include registers, register files, andmemory locations. In one embodiment, the shuffle PSHUFB instruction isdecoded into one micro-operation. In an alternative embodiment, theinstruction may be decoded into a various number of micro-ops to performthe shuffle operation on the data operands. For this example, theoperands 510, 520, are 128 bit wide pieces of information stored in asource register/memory having byte wide data elements. In oneembodiment, the operands 510, 520, are held in 128 bit long SIMDregisters, such as 128 bit SSE2 XMM registers. However, one or both ofthe operands 510, 520, can also be loaded from a memory location. Forone embodiment, the RESULTANT 540 is also a MMX or XMM data register.Furthermore, RESULTANT 540 may also be the same register or memorylocation as one of the source operands. Depending on the particularimplementation, the operands and registers can be other widths such as32, 64, and 256 bits, and have word, doubleword, or quadword sized dataelements. The first operand 510 in this example is comprised of a set ofsixteen masks (in hexadecimal format): 0x0E, 0x0A, 0x09, 0x8F, 0x02,0x0E, 0x06, 0x06, 0x06, 0xF0, 0x04, 0x08, 0x08, 0x06, 0x0D, and 0x00.Each individual mask is to specify the contents of its correspondingdata element position in the resultant 540.

The second operand 520 is comprised of sixteen data segments: P, O, N,M, L, K, J, I, H, G, F, E, D, C, B, and A. Each data segment in thesecond operand 520 is also labeled with a data element position value inhex format. The data segments here are of equal length and each compriseof a single byte (8 bits) of data. If each data element was a word (16bits), doubleword (32 bits), or a quadword (64 bits), the 128 bitoperands would have eight word wide, four doubleword wide, or twoquadword wide data elements, respectively. However, another embodimentof the present invention can operate with other sizes of operands anddata segments. Embodiments of the present invention are not restrictedto particular length data operands, data segments, or shift counts, andcan be sized appropriately for each implementation.

The operands 510, 520, can reside either in a register or a memorylocation or a register file or a mix. The data operands 510, 520, aresent to the shuffle logic 530 of an execution unit in the processoralong with a shuffle instruction. By the time the shuffle instructionreaches the execution unit, the instruction should have been decodedearlier in the processor pipeline. Thus the shuffle instruction can bein the form of a micro operation (uop) or some other decoded format. Forthis embodiment, the two data operands 510, 520, are received at shufflelogic 530. The shuffle logic 530 selects data elements from the sourcedata operand 520 based on the values in the mask operand 510 andarranges/shuffles the selected data elements into the appropriatepositions in the resultant 540. The shuffle logic 530 also zeroes outthe given data element positions in the resultant 540 as specified.Here, the resultant 540 is comprised of sixteen data segments: O, K, J,‘0’, C, O, G, G, F, ‘0’, E, I, I, G, N, and A.

The operation of the shuffle logic 530 is described here with a couplefew of the data elements. The shuffle mask for the leftmost data elementposition in the mask operand 510 is 0x0E. The shuffle logic 530interprets the various fields of the mask described as above in FIG.3A-C. In this case, the ‘set to zero’ field is not set. The selectionfield, comprising the lower four bits or nibble, has a hex value of ‘E’.The shuffle logic 530 shuffles the data, O, in the data element position‘0xE’ of the data operand 520 to the leftmost data element position ofthe resultant 540. Similarly, the mask at the second leftmost dataelement position in the mask operand 510 is 0x0A. The shuffle logic 530interprets the mask for that position. This selection field has a hexvalue of ‘A’. The shuffle logic 530 copies the data, K, in the dataelement position ‘0xA’ of the data operand 520 to the second leftmostdata element position of the resultant 540.

The shuffle logic 530 of this embodiment also supports the flush to zerofunction of the shuffle instruction. The shuffle mask at the fourth dataelement position from the left for the mask operand 510 is 0x8F. Theshuffle logic 510 recognizes that the ‘set to zero’ field is set asindicated by a ‘1’ at bit 8 of the mask. In response, the flush to zerodirective trumps the selection field and the shuffle logic 510 ignoresthe hex value ‘F’ in the selection field of that mask. A ‘0’ is placedin the corresponding fourth data element position from the left in theresultant 540. For this embodiment, the shuffle logic 530 evaluates the‘set to zero’ and selection fields for each mask and does not care aboutthe other bits that may exist outside of those fields in the mask, suchas reserved bits or a source select field. This processing of theshuffle masks and data shuffling is repeated for the entire set of masksin the mask operand 510. For one embodiment, the masks are all processedin parallel. In another embodiment, a certain portion of the mask setand data elements can be processed together at a time.

With embodiments of the present shuffle instruction, data elements in anoperand can be rearranged in various ways. Furthermore, certain datafrom particular data element can be repeated at multiple data elementpositions or even broadcasted to every position. For instance, thefourth and fifth masks both have a hex value of 0x08. As a result, thedata, I, at data element position 0x8 of the data operand 520 isshuffled into both the fourth and fifth data element positions from theright side of the resultant 540. With the set to zero functionality,embodiments of the shuffle instruction can force any of the data elementpositions in the resultant 540 to ‘0’.

Depending on the particular implementation, each shuffle mask can beused to designate the content of a single data element position in theresultant. As in this example, each individual byte wide shuffle maskcorresponds to a byte wide data element position in the resultant 540.In another embodiment, combinations of multiple masks can be used todesignate blocks of data elements together. For example, two byte widemasks can be used together to designate a word wide data element.Shuffle masks are not restricted to being byte wide and can be any othersize needed in that particular implementation. Similarly, data elementsand data element positions can possess other granularities other thanbytes.

FIG. 6 is a block diagram of one embodiment of a circuit 600 forperforming a data shuffling operation in accordance with the presentinvention. The circuit of this embodiment comprises a multiplexingstructure to select the correct result byte from the first sourceoperand based on decoding shuffle mask of the second operand. The sourcedata operand here is comprised of the upper packed data elements and thelower packed data elements. The multiplexing structure of thisembodiment is relatively simpler than other multiplexing structures usedto implement other packed instructions. As a result, the multiplexingstructure of this embodiment does not introduce any new critical timingpath. The circuit 600 of this embodiment includes a shuffle mask block,blocks to hold lower/upper packed data elements from source operands, afirst plurality of eight to one (8:1) muxes for initial selection ofdata elements, another plurality of three to one (3:1) muxes forselection of upper and lower data elements, mux select & zero logic anda multitude of control signals. For simplicity, a limited number of the8:1 and 3:1 muxes are shown in FIG. 6 and represented by dots. However,their function is similar to those illustrated and can be understoodfrom the description below.

During a shuffle operation in this example, two operands are received atthis shuffle handling circuit 600: a first operand with a set of packeddata elements and a second operand with a set of shuffle masks. Theshuffle masks are propagated to shuffle mask block 602. The set ofshuffle masks are decoded at the mux select and zero logic block 604 togenerate a variety of select signals (SELECT A 606, SELECT B 608, SELECTC 610) and a set to zero signal (ZERO) 611. These signals are used tocontrol the operation of the muxes in piecing together the resultant632.

For this example, the mask operand and data operand are both 128 bitslong and each are packed with of sixteen byte size data segments. Thevalue N as shown on various signals is sixteen in this case. In thisembodiment, the data elements are separated into a set of lower andupper packed data elements, each set having eight data elements. Thisallows for the use of smaller 8:1 muxes during the data elementselection rather than 16:1 muxes. These lower and upper sets of packeddata elements are held at lower and upper storage areas 612, 622,respectively. Starting with the lower data set, each of the eight dataelements are sent to the first set of sixteen individual 8:1 muxes618A-D via a set of lines such as routing lines 614. Each of the sixteen8:1 muxes 618A-D are controlled with one of the N SELECT A signals 606.Depending on the value of its SELECT A 606, that mux is to output one ofthe eight lower data elements 614 for further processing. There aresixteen 8:1 muxes for the set of lower packed data elements as it ispossible to shuffle any of the lower data elements into any of thesixteen resultant data element positions. Each of the sixteen 8:1 muxesis for one of the sixteen resultant data element positions. Similarly,sixteen 8:1 muxes are present for the upper packed data elements. Theeight upper data elements are sent to each of the second set of sixteen8:1 muxes 624A-D. Each of the sixteen 8:1 muxes 624A-D are controlledwith one of the N SELECT B signals 608. Based on the values of itsSELECT B 608, that 8:1 mux is to output one of the eight upper dataelements 616 for further processing.

Each of the sixteen 3:1 muxes 628A-D corresponds to a data elementposition in the resultant 632. The sixteen outputs 620A-D from thesixteen lower data muxes 618A-D are routed to a set of sixteen 3:1upper/lower selection muxes 628A-D as are the outputs 626A-D from theupper data muxes 624A-D. Each of these 3:1 selection muxes 628D-Dreceives its own SELECT C 610 and a ZERO 611 signals from the mux select& zero logic 604. The value on the SELECT C 610 for that 3:1 mux is toindicate whether the mux is to output the selected data operand from thelower data set or from the upper data set. The control signal ZERO 611to each 3:1 mux is to indicate whether that mux should force its outputto zero (‘0’). For this embodiment, the control signal ZERO 611supercedes the selection on SELECT C 610 and forces the output for thatdata element position to ‘0’ in the resultant 632.

For example, 3:1 mux 628A receives the selected lower data element 620Afrom 8:1 mux 618A and the selected upper data element 626A from 8:1 mux624A for that data element position. SELECT C 610 controls which of thedata elements to shuffle at its output 630A into the data elementposition it manages in the resultant 632. However, if signal ZERO 611 tothe mux 628A is active, indicated that the shuffle mask for that dataelement position states that a ‘0’ is desired, the mux output 630A is‘0’ and neither of the data element inputs 620A, 626A, are used. Theresultant 632 of the shuffle operation is composed of the outputs 630A-Dfrom the sixteen 3:1 muxes 628A-D, wherein each output corresponds to aspecific data element position and is either a data element or a ‘0’. Inthis example, each 3:1 mux output is a byte wide and the resultant is adata block composed of sixteen packed bytes of data.

FIG. 7 illustrates the operation of a data shuffle on byte wide dataelements in accordance with one embodiment of the present invention.This is an example of the instruction “PSHUFB DATA, MASK”. Note that themost significant bit of shuffle masks for byte positions 0x6 and 0xC ofMASK 701 are set so the result in resultant 741 for those positions arezero. In this example, source data is organized into a destination datastorage device 721, which in one embodiment is also the source datastorage device 721, in view of a set of masks 701 that specify theaddress wherein respective data elements from the source operand 721 areto be stored in the destination register 741. The two source operands,mask 701 and data 721, each comprise of sixteen packed data elements inthis example, as does the resultant 741. In this embodiment, each of thedata elements involved is a eight bits or a byte wide. Thus mask 701,data 721, and resultant 741 data blocks are each 128 bits long.Furthermore, these data blocks can reside in memory or registers. Forone embodiment, the arrangement of the masks is based on the desireddata processing operation, which may include for example, a filteringoperation or a convolution operation.

As shown in FIG. 7, mask operand 701 includes data elements with shufflemasks of: 0x0E 702, 0x0A 703, 0x09 704, 0x8F 705, 0x02 706, 0x0E 707,0x06 708, 0x06 709, 0x05 710, 0xF0 711, 0x04 712, 0x08 713, 0x08 714,0x06 715, 0x0D 716, 0x00 717. Similarly, data operand 721 includessource data elements of: P 722, O 723, N 724, M 725, L 726, K 727, J728, I 729, H 730, G 731, F 732, E 733, D 734, C 735, B 736, A 737. Inthe representations of data segments of FIG. 7, the data elementposition is also noted under the data as a hex value. Accordingly, apacked shuffle operation is performed with the mask 701 and data 721.Using the set of shuffle masks 701, processing of the data 721 can beperformed in parallel.

As each of the data element shuffle masks are evaluated, the appropriatedata from the designated data element or a ‘0’ is shuffled to thecorresponding data element position for that particular shuffle mask.For instance, the right most shuffle mask 717 has a value 0x00, which isdecoded to designate data from position 0x0 of the source data operand.In response, data A from data position 0x0 is copied to the right mostposition of the resultant 741. Similarly, the second shuffle mask 716from the right has a value of 0x0D, which is decoded to be 0xD. Thusdata N from data position 0xD is copied to the second position from theright in the resultant 741.

The fourth data element position from the left in the resultant 741 is a‘0’. This is attributed to the value of 0x8F in the shuffle mask forthat data element position. In this embodiment, bit 7 of the shufflemask byte is a ‘set to zero’ or ‘flush to zero’ indicator. If this fieldis set, the corresponding data element position in the resultant isfilled with a ‘0’ value instead of data from the source data operand721. Similarly, the seventh position from the right in the resultant 741has a value of ‘0’. This is due to the shuffle mask value of 0xF0 forthat data element position in the mask 701. Note that not all bits inthe shuffle mask may be used in certain embodiments. In this embodiment,the lower nibble, or four bits, of a shuffle mask is sufficient toselect any of the sixteen possible data elements in the source dataoperand 721. As bit 7 is the ‘set to zero’ field, three other bitsremain unused and can be reserved or ignored in certain embodiments. Forthis embodiment, the ‘set to zero’ field controls and overrides the dataelement selection as indicated in the lower nibble of the shuffle mask.In both of these instances, the fourth data element position from theleft and the seventh position from the right, a shuffle mask value of0x80 wherein the ‘flush to zero’ flag is set at bit seven can also causethe corresponding resultant data element position to be filled with a‘0’.

As shown in FIG. 7, the arrows illustrate the shuffling of the dataelements per the shuffle masks in mask 701. Depending on the particularset of shuffle masks, one or more of the source data elements may notappear in the resultant 741. In some instances, one or more ‘0’s canalso appear at various data element positions in the resultant 741. Ifthe shuffle masks are configured to broadcast one or a particular groupof data elements, the data for those data elements may be repeated as achosen pattern in the resultant. Embodiments of the present inventionare not restricted to any particular arrangements or shuffle patterns.

As noted above, the source data register is also utilized as thedestination data storage register in this embodiment, thereby reducingthe number of registers needed. Although the source data 721 is thusoverridden, the set of shuffle masks 701 is not altered and is availablefor future reference. Overwritten data within the source data storagedevice can be reloaded from memory or another register. In anotherembodiment, multiple registers can be used as the source data storagedevice, with their respective data organized within the destination datastorage device as desired.

FIG. 8 illustrates the operation of a data shuffle operation on wordwide data elements in accordance with another embodiment of the presentinvention. The general discussion of this example is somewhat similar tothat of FIG. 7. In this scenario, however, the data elements of the dataoperand 821 and resultant 831 are word length. For this embodiment, thedata element words are handled as pairs of data element bytes as theshuffle masks in the mask operand 801 are byte size. Thus a pair ofshuffle mask bytes are used to define each data element word position.But for another embodiment, the shuffle masks can also have wordgranularity and describe word sized data element positions in theresultant.

The mask operand 801 of this example includes byte wide data elementswith shuffle masks of: 0x03 802, 0x02 803, 0x0F 804, 0x0E 805, 0x83 806,0x82 807, 0x0D 808, 0x0C 809, 0x05 810, 0x04 811, 0x0B 812, 0x0A 813,0x0D 814, 0x0C 815, 0x01 816, 0x00 817. The data operand 821 includessource data elements of: H 822, G 823, F 824, E 835, D 836, C 827, B828, A 829. In the representations of data segments of FIG. 8, the dataelement position is also noted under the data as a hex value. As shownin FIG. 8, each of the word size data elements in the data operand 821have data position addresses it occupies two byte size positions. Forexample, data H 822 takes up byte size data element positions 0xF and0xE.

A packed shuffle operation is performed with the mask 801 and data 821.The arrows in FIG. 8 illustrate the shuffling of the data elements perthe shuffle masks in mask 801. As each of the data element shuffle masksare evaluated, the appropriate data from the designated data elementposition of the data operand 821 or a ‘0’ is shuffled to thecorresponding data element position in the resultant 831 for thatparticular shuffle mask. In this embodiment, the byte size shuffle masksoperate in pairs in order to designate word size data elements. Forexample, the two leftmost shuffle masks 0x03 802, 0x02803, in the maskoperand 801 together correspond to the leftmost word wide data elementposition 832 of the resultant 831. During the shuffle operation, the twodata bytes, or single data word, at data element byte positions 0x03 and0x02, which in this case is data B 828, is arranged into the twoleftmost byte size data element positions 832 in the resultant 831.

Furthermore, the shuffle masks can also be configured to force a wordsize data element to ‘0’ in the resultant as shown with shuffle masks0x83 806 and 0x82 807 for the third word size data element position 834in the resultant 831. Shuffle masks 0x83 806 and 0x82 807 have their‘set to zero’ fields set. Although two shuffle mask bytes are pairedtogether here, different pairings can also be implemented to arrangefour bytes together as a quadword or eight bytes together to form adouble quadword, for example. Similarly, the pairings are not restrictedto consecutive shuffle masks or particular bytes. In another embodiment,word size shuffle masks can be used to designate word size dataelements.

FIG. 9 is a flow chart 900 illustrating one embodiment of a method toshuffle data. The length value of L is generally used here to representthe width of the operands and data blocks. Depending on the particularembodiment, L can be used to designate the width in terms of number ofdata segments, bits, bytes, words, etc. At block 910, a first length Lpacked data operand is received for use with a shuffle operation. Alength L set of M length shuffle masks designating a shuffle pattern isreceived at block 920. In this example, L is 128 bits and M is 8 bits ora byte. In another embodiment, L and M can also be other values, such as256 and 16, respectively. At block 930, the shuffle operation isperformed wherein data elements from the data operand are shuffledarranged into a resultant in accordance to the shuffle pattern.

The details of the shuffle at block 930 of this embodiment is furtherdescribed in terms of what occurs for each data element position. Forone embodiment, the shuffling for all of the packed resultant dataelement positions are processed in parallel. In another embodiment, acertain portion of the masks may be processed together at a time. Atblock 932, a check is made to determine whether a zero flag is set. Thiszero flag refers to the set/flush to zero field of each shuffle mask. Ifthe zero flag is determined as set at block 932, the entry at theresultant data element position corresponding to that particular shufflemask is set to ‘0’. If the zero flag is found not set at block 932, thedata from the source data element designated by the shuffle mask isarranged into the destination data element position of the resultantcorresponding to that shuffle mask.

Currently, table lookups using integer instructions requires a largenumber of instructions. An even greater number of instructions areneeded per lookup if integer operations are used to access data foralgorithms implemented with SIMD instructions. But by using embodimentsof a packed byte shuffle instruction, the instruction count andexecution time is drastically reduced. For instance, sixteen data bytescan be accessed during a table lookup with a single instruction if thetable size is sixteen bytes or less. Eleven SIMD instructions can beused to lookup table data if the table size is between seventeen andthirty two bytes. Twenty three SIMD instructions are needed if the tablesize is between thirty three and sixty four bytes.

There are some applications with data parallelism that cannot beimplemented with SIMD instructions due to their use of lookup tables.The quantization and deblocking algorithms of the video compressionmethod H.26L is an example of an algorithm that uses small lookup tablesthat may not fit into a 128 bit register. In some cases, the lookuptables used by these algorithms are small. If the table can fit in asingle register, the table lookup operation can be accomplished with onepacked shuffle instruction. But if the memory space requirement of thetable exceeds the size of a single register, embodiments of a packedshuffle instruction can still work via a different algorithm. Oneembodiment of a method for handling oversized tables divides a tableinto sections, each equal to the capacity of a register, and accesseseach of these table sections with a shuffle instruction. The shuffleinstruction uses the same shuffle control sequence to access eachsection of the table. As a result, a parallel table lookup can beimplemented in these cases with the packed byte shuffle instruction,thus permitting the use of SIMD instructions to improve algorithmperformance. Embodiments of the present invention can help improveperformance and reduce the number of memory accesses needed foralgorithms that use small lookup tables. Other embodiments also permitaccess of multiple lookup table elements using SIMD instructions. Apacked byte shuffle instruction in accordance to the present inventionpermits efficient SIMD instruction implementation instead of lessefficient integer implantation of algorithms that use small lookuptables. This embodiment of the present invention demonstrates how toaccess data from a table that requires memory space larger than a singleregister. In this example, the registers contain different segments ofthe table.

FIGS. 10A-H illustrate the operation of a parallel table lookupalgorithm using SIMD instructions. The example described in FIGS. 10A-Hinvolves the lookup of data from multiple tables and wherein certainselected data elements as specified in a set of masks are shuffled fromthese multiple tables into a merged block of resultant data. Thediscussion below is explained in the context of packed operations,especially a packed shuffle instruction as disclosed in the earlierabove text. The shuffle operation of this example overwrites the sourcetable data in the register. If the table is to be reused following thelookup operation, the table data should be copied to another registerbefore the operation is executed so that another load is not needed. Inan alternative embodiment, the shuffle operation makes use of threeseparate registers or memory locations: two source and one destination.The destination in an alternative embodiment is a register or memorylocation that is different from either of the source operands. Thus, thesource table data is not overridden and can be reused. In this example,the table data is treated as coming from different portions of a largertable. For example, LOW TABLE DATA 1021 is from a lower address regionof the table and HIGH TABLE DATA 1051 is from a higher address region ofthe table. Embodiments of the present invention are not restrictive asto where the table data can originates. The data blocks 1021, 1051, canbe adjacent, far apart, or even overlapping. Similarly, table data canalso be from different data tables or different memory sources. It isalso envisioned that such a table lookup and data merging can beperformed on data from multiple tables. For instance, instead of comingfrom different parts of the same table, LOW TABLE DATA 1021 can be froma first table and HIGH TABLE DATA 1051 can be from a second table.

FIG. 10A illustrates a packed data shuffle of a first set of dataelements from a table based on a set of shuffle masks. This first set ofdata elements is grouped as an operand named LOW TABLE DATA 1021. MASK1001 and LOW TABLE DATA 1021 are each comprised of sixteen elements inthis example. A shuffle operation of MASK 1001 and LOW TABLE DATA 1021yields a resultant TEMP RESULTANT A 1041. The lower portion of a shufflecontrol mask selects the data element in the register. The number ofbits needed to select a data element is the number of register dataelements in log₂. For example, if the register capacity is 128 bits andthe data type is bytes, the number of register data elements is sixteen.In this case, four bits are need to select a data element. FIG. 10Billustrates a packed data shuffle of a second set of data elements froma table based on the same set of shuffle masks of FIG. 10A. This secondset of data elements is grouped as an operand named HIGH TABLE DATA1051. HIGH TABLE DATA 1051 is also comprised of sixteen elements in thisexample. A shuffle operation of MASK 1001 and HIGH TABLE DATA 1051yields a resultant TEMP RESULTANT B 1042.

Because the same set of masks 1001 were used with both the LOW TABLEDATA 1021 and HIGH TABLE DATA 1051, their respective resultants 1041,1042, appear to have similarly positioned data, but from differentsource data. For example, the leftmost data position of both resultants1041, 1042, have data from data element 0xE 1023, 1053, of itsrespective data source 1021, 1051. FIG. 10C illustrates a logical packedAND operation involving SELECT FILTER 1043 and the set of shuffle masksMASK 1001. SELECT FILTER in this case is a filter to distinguish whichof the shuffle masks in MASK 1001 are related to the first table data1021 and which to the second table data 1051. The shuffle masks of thisembodiment utilize the source select field, SRC SELECT 336, as discussedpreviously in FIG. 3C. Lower bits of a shuffle control byte are used toselect a data element position in a register and the upper bits,excluding the most significant bit, are used to select the segment ofthe table. For this embodiment, the bits immediately above and adjacentto those used to select the data select the section of the table. SELECTFILTER 1043 applies 0x10 to all the shuffle masks in MASK 1001 separateout the source select field from the shuffle masks. The packed ANDoperation yields a TABLE SELECT MASK 1044 that to indicate which dataelement position in the end resultant should be from the first data set1021 or the second data set 1051.

The number of bits to select the table section is equal to the number oftable sections in log₂. For example, in the case of table sizes rangingfrom seventeen to thirty two bytes with sixteen byte registers, thelowest four bits select the data and the fifth bit selects the tablesection. Here, source select uses the lowest bit of the second nibble,bit 4, of each shuffle mask to designate the data source as there aretwo data sources 1021, 1051. The section of the table with indicesbetween zero and fifteen is accessed with the packed shuffle instructionin FIG. 10A. The section of the table with indices between sixteen andthirty one is accessed with the packed shuffle instruction in FIG. 10B.The field that selects the section of the table is isolated from theshuffle control bytes/indices in FIG. 10C. In implementations with alarger number of data sources, additional bits may be needed the sourceselect fields. In the case of a thirty two byte table, the shufflecontrol bytes 0x00 to 0x0F would select table elements zero throughfifteen in the first table section and shuffle control bytes 0x10 to0x1F would select table elements sixteen through thirty one in thesecond table section. For instance, consider a shuffle control bytespecifies 0x19. The bit representation of 0x19 is 0001 1001. The lowerfour bits, 1001, select the ninth byte (counting from 0) and the fifthbit, which is set to 1, selects the second table of two tables. A fifthbit equal to 0 would select the first table.

A mask to selects data values accessed from the first table section withindices zero to fifteen is computed with a packed compare equaloperation for this embodiment in FIG. 10D by selecting the shufflecontrol bytes whose fifth bit is a zero. FIG. 10D illustrates a packed“compare equal operation” of LOW FILTER 1045 and TABLE SELECT MASK 1044.The low table select mask produced in FIG. 10D for the first tablesection selects data elements accessed from the first table section withanother packed shuffle operation. LOW FILTER 1045 in this instance is amask to pull out or highlight the data element positions indicated bythe shuffle masks as coming from the first data set 1021. If the sourceselect field is ‘0’ in this embodiment, then the data source is to beLOW TABLE DATA 1021. The compare equal operation yields a LOW TABLESELECT MASK 1046 with 0xFF values for the data element positions thathave a source select value of ‘0’.

A mask to selects data values accessed from the second table sectionwith indices sixteen to thirty one is computed with a packed compareequal operation in FIG. 10E by selecting the shuffle control bytes whosefifth bit is a one. FIG. 10E illustrates a similar compare equaloperation on HIGH FILTER 1047 and TABLE SELECT MASK 1044. The high tableselect mask produced in FIG. 10E for the second table section selectsdata elements accessed from the second table section with a packedshuffle operation. HIGH FILTER 1047 is a mask to pull out the dataelement position indicated by the source select fields of the shufflemask as coming from the second data set 1051. If the source select fieldis ‘1’ in this embodiment, then the data source is to be HIGH TABLE DATA1051. The compare equal operation yields a HIGH TABLE SELECT MASK 1048with 0xFF values for the data element position that have a source selectvalue of ‘1’.

The data elements selected from the two table sections are merged atFIG. 10F. At FIG. 10F, a packed AND operation on LOW TABLE SELECT MASK1046 and TEMP RESULTANT A 1041 is shown. This packed AND operationfilters out the selected shuffled data elements from the first data set1021 per the mask 1046 that is based on the source select fields. Forexample, the source select field in the shuffle mask 1002 for theleftmost data element position has a value of ‘0’ as shown in TABLESELECT MASK 1044. Accordingly, LOW TABLE SELECT MASK 1046 has a 0xFFvalue in that position. The and operation here in FIG. 10F between that0xFF and the data in the leftmost data element position causes the dataO to transfer to SELECTED LOW TABLE DATA 1049. On the other hand, thesource select field in the shuffle mask 1004 for the third data elementposition from the left has a value of ‘1’ to indicate that the data isto come from a source other than the first data set 1021. Accordingly,LOW TABLE SELECT MASK 1046 has a 0x00 value in that position. The andoperation here does not pass the data J to SELECTED LOW TABLE DATA 1049and that position is left empty as 0x00.

A similar packed AND operation on HIGH TABLE SELECT MASK 1048 and TEMPRESULTANT B 1042 is shown in FIG. 10G. This packed AND operation filtersout the selected shuffled data elements from the second data set 1051per the mask 1048. Unlike the packed AND operation described in FIG.10F, the mask 1048 allows data designated by the source select fields ascoming from the second set of data to pass to SELECTED HIGH TABLE DATA1050 while the other data element positions are left empty.

FIG. 10H illustrates the merging of the selected data from the firstdata set and the second data set. A packed logical OR operation isperformed on SELECTED LOW TABLE DATA 1049 and SELECTED HIGH TABLE DATA1050 to obtain MERGED SELECTED TABLE DATA 1070, which is the desiredresultant of the parallel table lookup algorithm in this example. In analternative embodiment, a packed addition operation to add togetherSELECTED LOW TABLE DATA 1049 and SELECTED HIGH TABLE DATA 1050 can alsoyield MERGED SELECTED TABLE DATA 1070. As shown in FIG. 10H, eitherSELECTED LOW TABLE DATA 1049 or SELECTED HIGH TABLE DATA 1050 has a 0x00value for a given data position in this embodiment. This is because theother operand that does not have the 0x00 value is to contain thedesired table data selected from the appropriate source. Here, theleftmost data element position in the resultant 1070 is O, which isshuffled data 1041 from the first data set 1021. Similarly, the thirddata element position from the left in the resultant 1070 is Z, which isshuffled data 1042 from the second data set 1051.

The method for looking up data in oversized tables in this exampleembodiment can be summarized generally with the following operations.First, copy or load the table data into registers. Table values fromeach table section are accessed with a packed shuffle operation. Thesource select fields that identify the table section are extracted fromthe shuffle masks. Compare-if-equal operations on the source selectfields with the table section number to determine which table sectionsare the appropriate sources for the shuffled data elements. Thecompare-if-equal operations provides masks to further filter out thedesired shuffled data elements for each table section. The desired dataelements from the appropriate table sections are merged together to formthe end table lookup resultant.

FIG. 11 is a flow chart illustrating one embodiment of a method toperform a table lookup using SIMD instructions. The flow described heregenerally follows the methodology of FIG. 10A-H, but is not restrictedas such. Some of these operations can also be performed in differentorder or using various types of SIMD instructions. At block 1102, a setof shuffle masks designating a shuffle pattern is received. Theseshuffle masks also include source fields to indicate from which table orsource to shuffle data elements to obtain the desired resultant. Atblock 1104, the data elements for a first portion of a table or a firstdata set is loaded. The first portion data elements are shuffled inaccordance to the shuffle pattern of block 1102 at block 1106. Dataelements for a second portion of a table or a second data set is loadedat block 1108. The second portion data elements are shuffled inaccordance to the shuffle pattern of block 1102 at block 1110. At block1112, table selects are filtered out from the shuffle masks. The tableselects of this embodiment involve the source select fields thatdesignate where a data element is supposed to originate from. At block1114, a table select mask is generated for the shuffled data from thefirst portion of the table. A table select mask is generated for theshuffled data from the second portion of the table at block 1116. Thesetable select masks are to filter out the desired shuffled data elementsfor specific data element positions from the appropriate table datasource.

At block 1118, data elements are selected from the shuffled data of thefirst table portion in accordance with a table select mask of block 1114for the first table portion. Data elements are selected at block 1120from the shuffled data of the second table portion in accordance withthe table select mask of block 1116 for the second table portion. Theshuffled data elements selected from the first table portion at block1118 and from the second table portion at block 1120 are merged togetherat block 1122 to obtain merged table data. The merged table data of oneembodiment includes data elements shuffled from both the first tabledata and the second table data. For another embodiment, the merged tabledata can include data looked up from more than two table sources ormemory regions.

FIG. 12 is a flow chart illustrating another embodiment of a method toperform a table lookup. At block 1202, a table having a plurality ofdata elements are loaded. A determination is made at block 1204 as towhether the table fits in a single register. If the table fits into asingle register, the table lookup is performed with a shuffle operationat block 1216. If the data does not fit into a single register, tablelookup is to be performed with shuffle operations for each relevantportion of the table at block 1206. A logical packed AND operation isperformed to obtain the bits or field that select the table portion ordata source. A “compare-if-equal” operation at block 1210 creates a maskto select table data from the relevant portions of the table to belooked up. At block 1212, a logical AND operation is used to look up andselect data items from the table sections. A logical OR operation mergesthe selected data at block 1214 to obtain the desired table lookup data.

One embodiment of the packed shuffle instruction is implemented into analgorithm for rearranging data between multiple registers using theflush to zero capability. The objective of a mix operation is to mergethe contents of two or more SIMD registers in a single SIMD register ina selected arrangement in which the positions of data in the resultantdiffer from their original position in the source operands. Selecteddata elements are first moved to desired result positions and unselecteddata elements are set to zero. The positions to which selected dataelements were moved for one register are set to zero in other registers.Consequently, a single one of the result registers may contain a nonzerodata item in a given data element position. The following generalinstruction sequence can be used to mix data from two operands:

-   -   packed byte shuffle DATA A, MASK A;    -   packed byte shuffle DATA B, MASK B;    -   packed logical OR RESULTANT A, RESULTANT B.

Operands DATA A and DATA B contain elements that are to be rearranged orset zero. Operands MASK A and MASK B contain shuffle control bytes thatspecify where data elements are to be moved and which data elements areto be set to zero. For this embodiment, data elements in destinationpositions not set to zero by MASK A are set to zero by MASK B anddestination positions not set to zero by MASK B are set to zero by MASKA. FIGS. 13A-C illustrates an algorithm for rearranging data betweenmultiple registers. In this example, data elements from two data sourcesor registers 1304, 1310, are shuffled together into an interleaved datablock 1314. The data blocks including masks 1302, 1308, source data1304, 1310, and resultants 1306, 1312, 1314, of this example are each128 bits long and composed of sixteen byte size data elements. However,alternative embodiments can include data blocks of other lengths havingvarious sized data elements.

FIG. 13A illustrates a first packed data shuffle operation of a firstmask, MASK A 1302, on a first source data operand, DATA A 1304. For thisexample, the desired interleaved resultant 1314 is to include aninterleaved pattern of one data element from a first data source 1304and another data element from a second data source 1310. In thisexample, the fifth byte of DATA A 1304 is to be interleaved with thetwelfth byte of DATA B 1310. MASK A 1302 includes a repeated pattern of“0x80” and “0x05” in this embodiment. The 0x80 value in this embodimenthas the set to zero field set, wherein the associated data elementposition is filled with ‘0’. The 0x05 value states that the associateddata element position for that shuffle mask should be arranged with dataF₁ from data element 0x5 of DATA A 1304. In essence, the shuffle patternin MASK A 1302 arranges and repeats data F1 at every other resultantdata element position. Here, data F1 is the single piece of data to beshuffled from DATA A 1304. In alternative embodiments, data from variousnumber of source data elements can be shuffled. Thus embodiments are notrestricted to patterns involving a single piece of data or anyparticular pattern. The arrangement combinations for mask patterns areopen to all kinds of possibilities. The arrows in FIG. 13A illustratethe shuffling of the data elements per the shuffle masks of MASK A 1302.RESULTANT A 1306 of this shuffle operation is thus comprised of apattern of ‘0’ and F₁ per the mask pattern 1302.

FIG. 13B illustrates a second packed data shuffle operation involving asecond mask, MASK B 1308, together with a second source data operand,DATA B 1310. MASK B 1308 includes a repeated pattern of “0x0C” and“0x80”. The 0x80 value causes the associated data position for thatshuffle mask to receive ‘0’. The 0xC0 value causes the resultant dataelement position corresponding to that shuffle mask to be arranged withdata M₂ from data element 0xC of DATA B 1310. The shuffle pattern ofMASK B 1308 arranges data M₂ to every other resultant data elementposition. The arrows in FIG. 13B illustrate the shuffling of the dataelements per the set of shuffle masks in MASK B 1308. RESULTANT B 1312of this shuffle operation is thus comprised of a pattern of ‘0’ and M₂per the mask pattern 1308.

FIG. 13C illustrates the merging of the shuffled data, RESULTANT A 1306and RESULTANT B 1312 to achieve INTERLEAVED RESULTANT 1314. The mergingis accomplished with a packed logical OR operation. The pattern of ‘0’values in RESULTANT A 1306 and RESULTANT B 1312 allow for theinterleaving of the M2 and F1 data values 1314. For example, at theleftmost data element position, the logical OR of ‘0’ and M2 results inM2 in the leftmost data element position of the resultant 1314.Similarly, at the rightmost data element position, the logical OR of F₁and ‘0’ results in F₁ in the rightmost data element position of theresultant 1314. Thus data from multiple registers or memory locationscan be rearranged into a desired pattern.

FIG. 14 is a flow chart illustrating one embodiment of a method torearrange data between multiple registers. Data is loaded from a firstregister or memory location at block 1402. The first register data isshuffled at block 1404 based on a first set of shuffle masks. At block1406, data is loaded from a second register or memory location. Thissecond register data is shuffled at block 1408 in accordance with asecond set of shuffle masks. The shuffled data from the first and secondregister shuffles are merged at block 1410 with a logical OR to arriveat an interleaved data block with data from the first and secondregister.

FIGS. 15A-K illustrates an algorithm for shuffling data between multipleregisters to generate interleaved data. This is an example of anapplication that interleaves planar color data. Image data is oftenprocessed in separate color planes and then these planes are laterinterleaved for display. The algorithm described below demonstratesinterleaving for red plane, green plane, and blue plane data as used byimage formats such as bitmaps. Numerous color spaces and interleavepatterns are possible. As such, this approach can easily be extended toother color spaces and formats. This example implements an often usedimage processing data format process wherein red (R) plane, green (G)plane, and blue (B) plane data are interleaved into an RGB format. Thisexample demonstrates how the flush to zero capability in accordance tothe present invention significantly reduces memory accesses.

Data from three sources are combined together in an interleaved fashion.More particularly, the data relates to pixel color data. For example,color data for each pixel can include information from red (R), green(G), and blue (B) sources. By combining the color information, thered/green/blue (RGB) data can be evaluated to provide the desired colorfor that particular pixel. Here, the red data is held in operand DATA A1512, the green data in data operand DATA B 1514, and the blue data inDATA C 1516. This arrangement can exist in an graphics or memory systemwhere data for each separate color is stored together or collectedseparately as in streaming data. In order to use this information inrecreating or displaying the desired image, the pixel data has to bearranged into an RGB pattern wherein all the data for a particular pixelis grouped together.

For this embodiment, a set of masks having predefined patterns are usedin interleaving together the RGB data. FIG. 15A illustrates as set ofmasks: MASK A 1502 having a first pattern, MASK B 1504 having a secondpattern, and MASK C 1506 having a third pattern. Data from each registeris to be spaced three bytes apart so that it can be interleaved withdata from the two other registers. Control bytes with hex values 0x80have the most significant bit set so that the corresponding byte isflushed to zero by the packed byte shuffle instruction. In each of thesemasks, every third shuffle mask is enabled to select a data element forshuffling while the two intervening shuffle masks have values of 0x80.The 0x80 value indicates that the set to zero fields in the masks forthose corresponding data element positions are set. Thus ‘0’s will beplaced in the data element positions associated with that mask. In thisexample, the mask patterns are to basically separate out the dataelements for each color in order to accomplish the interleaving. Forexample, when MASK A 1502 is applied to a data operand in a shuffleoperation, the MASK A 1502 causes six data elements (0x0, 0x1, 0x2, 0x3,0x4, 0x5) to be shuffled apart with two data element spaces between eachdata element. Similarly, MASK B 1504 is to shuffle apart data elementsat 0x0, 0x1, 0x2, 0x3, 0x4. MASK C 1506 is to shuffle apart dataelements at 0x0, 0x1, 0x2, 0x3, 0x4.

Note that in this implementation, the shuffle mask for each particularoverlapping data element position has two set to zero fields set and oneshuffle mask designating a data element. For example, referring to therightmost data element position for the three sets of masks 1502, 1504,1056, the shuffle mask values are 0x00, 0x80, and 0x80, for MASK A 1502,MASK B 1504, and MASK C 1506, respectively. Thus only the shuffle mask0x00 for MASK A 1502 will specify data for this position. The masks inthis embodiment are patterned so that the shuffled data can be easilymerged to form the interleaved RGB data block.

FIG. 15B illustrates the blocks of data to be interleaved: DATA A 1512,DATA B 1514, and DATA C 1516. For this embodiment, each set of data hasan data entry with color information for sixteen pixel positions. Here,the subscript notion accompanying each color letter in a data elementrepresents that pixel number. For instance, R0 is the red data for pixel0 and G15 is the green data for pixel 15. The hex values at each dataelement illustrated is the number of that data element position. Thecolor data (DATA A 1512, DATA B 1514, DATA C 1516) may be copied intoother registers so that the data is not overwritten by the shuffleoperation and can be reused without another load operation. In theexample of this embodiment, three passes with the three masks 1502,1504, 1506, are needed to complete the pixel data interleaving. Foralternate implementations and other amounts of data, the number ofpasses and shuffling operations can vary as needed.

FIG. 15C illustrates the resultant data block, MASKED DATA A 1522, for apacked shuffle operation on red pixel data, DATA A 1512, with the firstshuffle pattern, MASK A 1502. In response to MASK A 1502, the red pixeldata is arranged into every third data element position. Similarly, FIG.15D illustrates the resultant data block, MASKED DATA B 1524 for apacked shuffle operation on green pixel data, DATA B 1514, with thesecond shuffle pattern, MASK B 1504. FIG. 15E illustrates the resultantdata block, MASKED DATA C 1526 for a shuffle operation on blue pixeldata, DATA C 1516, with a third shuffle pattern, MASK C 1506. For themask patterns of this embodiment, the resultant data blocks from theseshuffle operations provide data elements that are staggered so that oneof the data elements has data while two have ‘0’s. For instance, theleftmost data element position of these resultants 1522, 1524, 1526,contain R₅, ‘0’, and ‘0’, respectively. At the next data elementposition, the pixel data for another one of the RGB colors is presented.Thus when merged together, a RGB type of grouping is achieved.

In this embodiment, the above shuffled data for the red data and thegreen data are first merged together with a packed logical OR operation.FIG. 15F illustrates the resultant data, INTERLEAVED A & B DATA 1530,for the packed logical OR-ing of MASKED DATA A 1522 and MASKED DATA B1524. The shuffled blue data is now merged together with the interleavedred and green data with another packed logical OR operation. FIG. 15Gillustrates the new resultant, INTERLEAVED A, B, & C DATA 1532, from thepacked logic OR-ing of MASKED DATA C 1526 and MASKED DATA A & B 1530.Thus the resultant data block of FIG. 15G contains the interleaved RGBdata for the first five pixels and a portion of the sixth pixel.Subsequent iterations of the algorithm of this embodiment will yield theinterleaved RGB data for the rest of the sixteen pixels.

At this point, one third of the data in DATA A 1512, DATA B 1514, andDATA C 1516 has been interleaved. Two approaches can be used to processthe remaining data in these registers. Another set of shuffle controlbytes can be used to arrange the data to be interleaved or the data inDATA A 1512, DATA B 1514, and DATA C 1516 can be shifted right so thatthe shuffle masks 1502, 1504, 1506, can be used again. In theimplementation shown here, data is shifted to avoid making the memoryaccesses required to load additional shuffle control bytes. Withoutthese shifting operations, nine sets of control bytes would be needed inthis embodiment instead of three (MASK A 1502, MASK B 1504, MASK C1506). This embodiment can also be applied in architectures where alimited number of registers are available and memory accesses are long.

In alternative embodiments where a large number of registers areavailable, keeping all or a large number of mask sets in registers sothat shift operations are not necessary can be more efficient.Furthermore, in an architecture with many registers and execution units,all of the shuffle operations can be performed in parallel withouthaving to wait for the shifting to occur. For instance, an out-of-orderprocessor with nine shuffle units and nine mask sets can perform nineshuffle operations in parallel. In the embodiment above, the data has tobe shifted before the masks are reapplied.

The data elements in the original color data of DATA A 1512, DATA B1514, and DATA C 1516, are shifted in accordance to the number of dataelements already processed for that particular color. In this example,data for six pixels has been processed above for red, so the dataelements for red data operand DATA A 1512 is shifted to the right by sixdata element positions. Similarly, data for five pixels has beenprocessed for both green and blue, so the data elements for green dataoperand DATA B 1514 and for blue data operand DATA C 1516 are shiftedright by five data element positions each. The shifted source data isillustrated as DATA A′ 1546, DATA B′ 1542, and DATA C′ 1544, for thecolors red, green, and blue, respectively, in FIG. 15H.

The shuffle and logical OR operations as discussed above with FIG. 15A-Gare repeated with this shifted data. Subsequent packed shuffleoperations on DATA B′ 1542, DATA C′ 1544, and DATA A′ 1546, togetherwith MASK A 1502, MASK B 1504, and MASK C 1506, respectively, incombination with packed logical OR operations on the three packedshuffle resultants, provides interleaved RGB data for another fourpixels and parts of another two. This resultant data, INTERLEAVED A′,B′, AND C′ DATA 1548 is illustrated in FIG. 15I. Note that the rightmosttwo data elements relate to the sixth pixel, which already had its reddata R₅ arranged with the first interleaved data set 1532. The raw pixelcolor data is shifted again by the appropriate number of places per theprocessing results of the second pass. Here, data for five additionalpixels has been processed for red and blue, so the data elements for reddata operand DATA A′ 1546 and for blue data operand DATA C′ 1544 areshifted to the right by five data element positions. Data for six pixelshas been processed for green, so the data elements for green dataoperand DATA B′ 1542 is shifted to the right by six positions. Theshifted data for this third pass is illustrated in FIG. 15J. A repeat ofthe packed shuffle and logical OR operations above are applied to DATAC″ 1552, DATA A″ 1554, and DATA B″ 1556. The resultant interleaved RGBdata for the last of the sixteen pixels is illustrated in FIG. 15K asINTERLEAVED A″, B″ DATA 1558. The rightmost data element with B10relates to the eleventh pixel, which already has its green data G10 andred data R10 arranged with the second interleaved data set 1548. Thus,by way of a series of packed shuffle with a set of mask patterns andpacked logical OR operations, data from multiple sources 1512, 1514,1516, can be merged and rearranged together in a desired fashion forfurther use or processing like these resultants 1532, 1548, 1558.

FIG. 16 is a flow chart illustrating one embodiment of a method toshuffle data between multiple registers to generate interleaved data.For example, embodiments of the present method can be applied to thegeneration of interleaved pixel data as discussed in FIG. 15A-K.Although the present embodiment is described in the context of threedata sources or planes of data, other embodiments can operate with twoor more planes of data. These planes of data can include color data forone or more image frames. At block 1602, frame data for a first, second,and third plane are loaded. In this example, RGB color data for aplurality of pixels are available as individual colors from threedifferent planes. The data in the first plane is for the color red, thedata in the second plane is for green, and the data in the third planeis for blue. At block 1604, a set of masks with shuffle control patterns(M1, M2, and M3) are loaded. These shuffle control patterns determinethe shuffle patterns and arrangement of data in order to interleave thecolors together. Depending on the implementation, any number of shufflepatterns can be employed in order to generate the desired dataarrangement.

At block 1606, an appropriate control pattern is selected for each planeof data. In this embodiment, the shuffle pattern is selected based onwhich order the color data is desired and which iteration is presentlybeing executed. The frame data from the first data set, red, is shuffledwith a first shuffle control pattern at block 1608 to obtain shuffledred data. The second data set, green, is shuffled at block 1610 with asecond shuffle control pattern to obtain shuffled green data. At block1612, the third data set, blue, is shuffled with a third shuffle controlpattern to achieve shuffled blue data. Although the three masks andtheir shuffle control patterns are different from each other in thisembodiment, a mask and its shuffle pattern can be used on more than asingle data set during each iteration. Furthermore, some masks may beused more often than others.

At block 1614, the shuffled data of blocks 1608, 1610, 1612, for thethree data sets are merged together to form the interleaved resultantfor this pass. For example, the resultant of the first pass can looklike the interleaved data 1532 of FIG. 15G, wherein the RGB data foreach pixel is grouped together as a set. At block 1616, a check is madeto determine whether there is more frame data loaded in the registers toshuffling. If not, a check is made at block 1620 to determine whetherthere is more data from the three planes of data to be interleaved. Ifnot, the method is done. If there is more plane data available at block1620, the process proceeds back to block 1602 to load more frame datafor shuffling.

If the determination at block 1616 is true, the frame data in each planeof color data is shifted by a predetermined count that corresponds towhichever mask pattern was applied to the data set for that particularcolor during the last pass. For example, in keeping with the first passexample from FIG. 15G, the red, green, and blue data in the first,second, and third planes are shifted six, five, and five positions,respectively. Depending on the implementation, the shuffle patternselected for each color data may be different each pass or the same onereused. During the second pass for one embodiment, the three masks fromthe first iteration are rotated such that first plane data is now pairedwith the third mask, second plane data is paired with the first mask,and third plane data is paired with the third mask. This mask rotationallows for the proper continuity of interleaved RGB data from one passto the next, as illustrated in FIGS. 15G and 15I. The shuffling andmerging continues as in the first pass. Should a third or moreiterations be desired, the shuffle mask patterns of this embodimentcontinue to be rotated among the different planes of data in order togenerate more interleaved RGB data.

Embodiments of algorithms using packed shuffle instructions inaccordance with the present invention can also improve processor andsystem performance with present hardware resources. But as technologycontinues to improve, embodiments of the present invention when combinedwith greater amounts of hardware resources and faster, more efficientlogic circuits, can have an even more profound impact on improvingperformance. Thus, one efficient embodiment of a packed shuffleinstruction having byte granularity and a flush to zero option can havedifferent and greater impact across processor generations. Simply addingmore resources in modern processor architectures alone does notguarantee better performance improvement. By also maintaining theefficiency of applications like one embodiment of the parallel tablelookup and the packed byte shuffle instruction (PSHUFB), largerperformance improvements can be possible.

Although the examples above are generally described in the context of128 bits wide hardware/registers/operands to simplify the discussion,other embodiments employ 64 or 128 bits wide hardware/registers/operandsto perform packed shuffle operations, parallel table lookups, andmultiple register data rearrangement. Furthermore, embodiments of thepresent invention are not limited to specific hardware or technologytypes such as MMX/SSE/SSE2 technologies, and can be used with other SIMDimplementations and other graphical data manipulating technologies.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made thereofwithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense.

1. A processor for shuffling data comprising: a decoder to decode ashuffle instruction; a register file including an integer register and afloating point register; a register renaming logic to rename theregisters in the register file for the decoded instruction, the registerfile comprising a first 64-bit source register to store a first operandthat comprises four data elements, a second 64-bit register to store asecond source operand comprising a set of four 2-bit selection fieldsand a set of source select fields to indicate from the first sourceregister of a plurality of source data registers a data element is to beprovided, and a 64-bit destination register; a queue to store theregister renamed instruction; a scheduler to schedule execution ofoperations of the register renamed instruction based on the readiness ofthe dependent operands in the source registers; an execution unitoperative to receive from the register file the first operand and theset of selection fields, wherein each of said selection fields isassociated with a data element location in the destination operand, andeach of said selection fields being a position selection filed operativeto select one of said data elements from the first operand to be copiedto the destination operand; said execution unit is also operative to:copy data from a data element of the first operand based on an orderdesignated by said individual 2-bit selection field to said associateddestination data element position.
 2. The processor of claim 1, whereineach of the data elements of the second source operand further comprisesa flush to zero field, said flush to zero field to indicate whether adata element position associated with this control element is to befilled with a zero value.
 3. The processor of claim 2, wherein each ofsaid flush to zero fields is associated with a similarly located dataelement position in the destination operand.
 4. The processor of claim2, comprising a set of multiplexers coupled to said execution unit,wherein each multiplexer is also associated with a unique destinationdata element position, each multiplexer to output a zero if itsassociated flush to zero signal is active and to output data shuffledfrom a set of data elements based on its associated select field if itsassociated flush to zero signal is inactive.
 5. The processor of claim 4further comprising a register with unique data element positions, eachdata element position to hold an output from its associated multiplexer.6. The processor of claim 1, wherein the execution unit further todetermine whether each flush to zero field is set, and place a zero intoan associated destination data element position if true, otherwiseshuffle data from a first operand data element designated by saidindividual selection field to said associated destination data elementposition.
 7. The processor of claim 1 wherein said selection fields areto designate a first operand data element by a data element positionnumber.
 8. The processor of claim 1, the execution unit further tooutput a resultant data block comprising data that was shuffled fromsaid first operand in response to said selection fields of said secondoperand.
 9. The processor of claim 1, wherein said first operand, saidsecond operand, and said destination operand are each comprised of64-bit wide packed data.
 10. The processor of claim 1 wherein saidshuffle instruction is to further cause said execution unit to generatethe destination operand having each data element positions that havebeen filled based on said set of selection fields.
 11. The processor ofclaim 1 wherein said first source register and said second register area single instruction multiple data registers.